The present invention relates to an antenna device for a direction finder, and more particularly to a type of antenna device having an antenna which is held stationary.
An antenna for a direction finder which includes an electrically conductive plate in a square configuration, for example disposed in parallel with an electrically conductive base plate of a sufficient size with there being a predetermined space maintained between the two plates, is known. In the known antenna one corner of the antenna plate is connected to the base plate through a resistor having a resistance equal to the characteristic impedance of the antenna, while a diagonally opposite corner of the antenna plate is connected to a receiver of the direction finder through a cable having the characteristic impedance. Since the antenna as above described provides an output characteristic in the form of a cardioid against an electromagnetic wave arriving in parallel with the antenna plate, it can be used in combination with a direction finding unit to determine the arriving direction of the electromagnetic wave. However, the known construction of such antenna devices has included a rotating mechanism for rotating the antenna in determining the arriving direction, or in following automatically the variation of the arriving direction of the electromagnetic wave. Accordingly, the device has been complicated, causing various disadvantages including susceptibility to troubles and poor precision.